Buyer's Guide: Direct Boxes (DI Boxes)

A direct box, or DI box, is an essential piece of equipment for any recording or live sound setup. It’s used to convert an unbalanced, high-impedance instrument or line-level signal into a balanced, low-impedance signal that can be sent to a mixing console, audio interface, or other gear. But with so many different types of DI boxes on the market, it can be difficult to know which one is right for you. 

In this buyer's guide, we’ll break down everything you need to know about DI boxes, including the different types of signals they can handle, the different types of connectors and inputs they have, and the various features they offer. Let’s get started!

TYPES OF DI BOXES

Whether you're a musician, producer, or sound engineer, a good DI box is a must-have tool that can help you get the best sound possible. There are several different types of DI boxes to choose from, each with their own set of features and benefits. Let’s take a look at some of the most common types of DI boxes.

PASSIVE DI BOXES

Passive DI boxes are the most basic type of direct box. Since they rely on the power from the instrument to function, they don’t require any external power, which can be especially handy when performing on stage. Passive DI boxes are known for their warmth and character, thanks to the transformer that sits at the heart of the design. The transformer helps to isolate the input signal from ground loops and other forms of interference, while also adding a unique coloration to the sound that can be desirable in certain situations.

Suggested passive DI boxes: Acme Audio Motown D.I. WB-3, Walrus Audio Canvas Stereo Dual Line Isolator D.I., Radial ProDI, Radial JDI MK3, BAE PDI, Warm Audio Passive Direct Box, Telefunken Active Mono DI

ACTIVE DI BOXES

Unlike passive designs, active DI boxes require an external power source, usually in the form of a battery or power supply. They use active electronics to boost and balance the signal. This results in a more transparent and accurate sound, but can sometimes lack the warmth and character of transformer-based DI boxes. That’s what some active DI boxes include tubes and other Class A circuitry for added color. Active DI boxes are a popular choice for musicians who need to drive long cable runs or need more output level. 

Suggested active DI boxes: Rupert Neve Designs RNDI Active Transformer DI, Countryman Type 85, Avalon U5, Warm Audio Active Direct Box, Telefunken Active Mono DI, Radial J48, Radial Engineering HDI, A Designs Audio REDDI, Teegarden Audio Fatboy Tube DI, Demeter VTDB-2B 

RACKMOUNT DI BOXES

Rackmount DI boxes are designed to be mounted in a standard 19-inch equipment rack. They’re typically larger than other types of DI boxes and offer more features, such as multiple channels and advanced connectivity options. Rackmount DI boxes are ideal for live sound engineers and studio professionals who need multiple inputs and outputs. 

Suggested rackmount DI boxes: TK Audio Transceiver, Radial Engineering ProD8, Radial JD7 Injector, A Designs REDDI v2

RE-AMPLIFYING DI BOXES

Re-amplifying DI boxes provide a way to re-amplify the direct signal from an electric guitar or bass. They’re typically used in the studio to experiment with different tones, but can also be used in some live sound situations, like when a guitarist wants to send a direct signal to front of house and use an amp as a stage monitor.

Suggested re-amplifying DI boxes: UnderToneAudio GB Tracker, Radial Engineering EXTC-Stereo, Radial X-Amp, Little Labs Redeye 3D Phantom, IK Multimedia TONEX Capture Modeling DI and Reamp Box

SIGNAL BOOSTER DI BOXES

Signal boosters are a specialized type of DI box that are designed to boost weak microphone signals before they are sent to a preamp or audio interface. These devices typically feature a single XLR input and output, and use a combination of active electronics and transformer-based technology to boost the level of the incoming signal by up to 25dB. 

Signal boosters are ideal for use with ribbon microphones, which have a naturally low output level, or for situations where a microphone needs to be placed at a distance from the preamp. They’re also great for capturing quiet sources such as acoustic guitar, vocals, and drums without adding any noise or distortion. These devices are simple to use, plug-and-play, and they will help you to get more gain out of your microphone.

Suggested signal booster DI boxes: Cloud Microphones Cloudlifter CL-ZI, Royer Labs dBooster2, Soyuz Launcher and Launcher Deluxe

FEATURES TO CONSIDER

Now that we’ve covered the different types of DI boxes, let’s talk about some of the different features you should consider to ensure you find the right one for your needs.

INPUT AND OUTPUT OPTIONS

The first thing to consider is the input and output options available on the DI box. Most DI boxes will feature XLR and 1/4" TRS inputs and outputs, but some may also offer other options such as RCA or 1/8" TRS. Be sure to check that the DI box you choose has the input and output options that are compatible with your gear. You may also want to consider picking up a stereo DI for stereo signals like keyboards and amp simulators. 

IMPEDANCE MATCHING

Impedance matching is an important feature to consider when looking for a DI box. Impedance refers to the resistance of an electrical circuit, and mismatched impedance can cause signal loss or distortion. A DI box with impedance-matching capabilities will help ensure a clean, clear signal transfer between your gear and your audio interface.

GROUND LIFT

Another feature to consider is a ground lift switch. This switch disconnects the ground connection between the input and output, which can help eliminate ground loop noise in your signal. This is especially useful when dealing with hum or buzz caused by ground loops—a common occurrence for touring musicians playing different venues every night.

PHASE INVERSION

A phase inversion switch can also be a useful feature on a DI box. This switch allows you to reverse the polarity of the input signal, which can help fix phase issues that may be causing problems with your audio.

PAD SWITCH

A pad switch is another feature that can be helpful when using a DI box. This switch allows you to lower the input level of the signal, which can be useful when dealing with hot input signals that may cause distortion.

POWER OPTIONS

Finally, be sure to consider the power options available on the DI box. Some DI boxes are powered by batteries, while others may require phantom power from your audio interface. Battery-powered DI boxes offer great portability and can be used everywhere, but can also cause problems if the battery runs out during a performance. Alternatively, powered DI boxes offer more consistency, but won’t work without an outlet. Be sure to choose a DI box that is compatible with your power needs.

When it comes to purchasing a DI box, it's important to first consider the specific needs of your recording setup. Whether you're a professional engineer working in a large studio or a home recording enthusiast, a high-quality DI box can bring significant improvement to your recordings.

When choosing a DI box, it's important to consider the types of inputs and outputs you'll need, as well as features such as impedance matching, ground lift, phase inversion, and pad switching. Additionally, consider the power options available and choose a DI box that will work seamlessly with your existing equipment.

Ultimately, investing in a high-quality DI box will not only improve the sound quality of your recordings, but it will also make your workflow more efficient and effective. With the wide range of options available on the market, it's important to do your research and choose a DI box that meets your specific needs and budget.

If you have questions about DI boxes for your studio or live rig, we're here to help! Please contact a Vintage King Audio Consultant via email or by phone at 866.644.0160.